Diabetic retinopathy remains the leading cause of new blindness in the 20-60 year old age group, in spite of the proven efficacy of a number of therapies. Annual surveillance of patients with diabetes by an ophthalmologist is recommended to detect retinopathy sufficiently early to prevent serious visual impairment. Patient compliance with this guideline has generally been poor. An alternative approach is to screen patients in the offices of primary care physicians in conjunction with routine visits. However, no screening procedures of proven efficacy are yet available. The goal of this research is to develop a series of screening options or protocols to detect by fundus examination patients with diabetes requiring ophthalmological referral because of the presence of, or high likelihood of developing, vision threatening retinopathy [defined for this purpose as proliferative diabetic retinopathy (PDR) or macular edema (ME)]. The screening options will be developed from an analysis of the fundus photographic data set from the Early Treatment Diabetic Retinopathy Study (ETDRS). The objective is to determine whether the examination of a limited portion of the posterior fundus for retinopathy lesions can provide sufficient information to predict vision threatening retinopathy in the fundus region defined by the seven standard photographic fields. The specific aim is to determine which diabetic lesions, of what severity level, and in which of the posterior photographic fields are the best predictors of PDR or ME; statistical regression techniques will be used to identify the most significantly correlated variables. The screening criteria comprising the optimal Receiver Operator Characteristics (ROC curves), i.e. the criteria with the best sensitivity (true positive rate) and specificity (true negative rate) will be identified.